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<head>
  <meta charset="UTF-8">
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  <title>Document</title>
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<body>
  <script>
    var obj = { name: "why" }
    function foo() {
      console.log('foo函数:', this)
    }

    // 执行函数,并且函数中的this指向obj对象
    obj.foo = foo
    obj.foo()

    // 执行函数,并且强制this就是obj对象
    foo.call(obj)
    foo.call(123)
    foo.call("abc")
    foo.call(undefined) // 特殊情况->window

  </script>
</body>

</html>